The present invention relates to a drive gear for a motor vehicle or the like having a starter disc with a hub, with which the drive gear is connected to a shaft of a vehicle motor for joint rotation therewith, and a drive ring, which is secured on the starter disc for joint rotation therewith and is connected to a converter of the automatic transmission of the vehicle for joint rotation with he converter.
Such drive gears serve, on one hand, for starting the vehicle motor and, on the other hand, for transmitting the drive force from the motor, via a converter, to the transmission. To this end, the drive ring is bulged outwardly in the region of the openings, which insure its connection to the converter, so that it can take up, in a mounted condition, certain axial and radial forces. The drive ring is formed as a one-piece element and is secured to the starter disc during assembly of the vehicle. The drawback of this known drive gear consists in that, in addition to the assembly costs, the drive ring, because of convexity of the starter disc, has a reduced stability in the region where it is connected to the converter. The reduced stability is compensated by an increased wall thickness, so that the drive ring weight is relatively high. The increased wall thickness leads also to an increased space requirement for the drive ring, which is also a drawback.
To overcome these drawbacks, it was suggested to form the drive gear as a one-piece part in which the toothing was provided directly on drive ring, or as a two-piece part, in which a toothed ring is connected with the drive element. The suggested one-piece drive gear is indeed very rigid and does not lead to increased assembly cost, however, it was found that such rigid drive gear can take up only small translational and rotational forces. With large forces, the hub region of the drive gear cracks and the drive gear need be replaced.
It was further suggested to form the starter disc and the drive element as separate parts with their own hubs. The drawback of this two-part design consists in increased assembly costs, because of necessity to assemble two parts. In addition, such a two-part drive gear has an increased weight. To reduce the weight, both the drive element and the starter disc can be formed with a reduced wall thickness. However, the reduced wall thickness leads to that the starter disc takes up negative vibrations of the vehicle motor.
Accordingly, the main object of the invention is a drive gear which would have a reduced weight, is easy to assemble, requires small mounting space, is operationally reliable, and is flexible with regard to axial forces acting thereon, and which can assume additional functions.